Novel Approach to Measuring Tensile Strength of Compacted Clayey Soil during Desiccation

Abstract

Desiccation of soil is the gradual process of moisture loss from a fully or partially saturated condition to a dry state. If the soil is constrained against shrinkage during desiccation, it will begin to crack when tensile stresses in the soil exceed the tensile strength. Fundamental to understanding desiccation crack development in clayey soils is the accurate determination of the tensile strength during desiccation. Although numerous published studies have focused on soil desiccation and soil tensile strength, very little has been focused on experimental determination of tensile strength during desiccation. This paper presents the first generation of a novel apparatus designed to determine tensile strength during desiccation. During drying the tensile forces in a thin compacted soil layer are measured while simultaneously monitoring moisture content changes and crack formation via time-lapse photography. Results are presented from desiccation tests performed on two clayey compacted soils of medium to high plasticity. Soil water characteristic curves (SWCCs) were determined to relate the tensile strength to suction. The results demonstrate that the tensile strength of compacted soil is influenced by initial water content, suction, dry unit weight, soil pore structure, and soil type. Measured tensile strengths compare favorably with results of a theoretical model that considers microstructural and macrostructural aspects of unsaturated compacted clayey soil.